Press release from Major League Baseball: the new home plate collision rule is out. It’s Rule 7.13 .It reads as follows:

A runner attempting to score may not deviate from his direct pathway to the plate in order to initiate contact with the catcher (or other player covering home plate). If, in the judgment of the Umpire, a runner attempting to score initiates contact with the catcher (or other player covering home plate) in such a manner, the Umpire shall declare the runner out (even if the player covering home plate loses possession of the ball).

Unless the catcher is in possession of the ball, the catcher cannot block the pathway of the runner as he is attempting to score. If, in the judgment of the Umpire, the catcher, without possession of the ball, blocks the pathway of the runner, the Umpire shall call or signal the runner safe.

That seems fairly straight-forward. Major League Baseball added this, however, as explanation:

In determining whether a runner deviated from his pathway in order to initiate a collision, the Umpire will consider whether the runner made an effort to touch the plate, and whether he lowered his shoulders or pushed through with his hands, elbows or arms when veering toward the catcher. The rule that will be in effect in 2014 does not mandate that the runner always slide or that the catcher can never block the plate. However, runners who slide, and catchers who provide the runner with a lane to reach the plate, will never be found to be in violation of the new rule. Beginning immediately, Clubs will be required to train their runners to slide and their catchers to provide the runner with a pathway to reach the plate at all levels in their organizations.

Also: instant replay will apply to Rule 7.13 interpretations. The league will be going around spring training to apprise every team of the rules and to answer questions.